Northern exposure - Deep energy retrofit transforms north-facing Dublin seaside semi

€125 per month for all energy
Building: Deep retrofit & extension of 1960s cavity wall house
Location: Blackrock, Co Dublin
Standard: A3

If you’re an experienced architect who has taken the opportunity in recent years to learn about building performance and energy efficiency, the chances are it will have a seismic impact on the way you design any future projects.

One upshot is that projects like this attractive retrofit of a 1960s four-bed semi-detached house in Blackrock, Co Dublin, are all about achieving an equal balance between quality design and thermal performance.

The rear of the house is north facing but with probably one of the best views anywhere of Dublin Bay, taking in the iconic red and white twin chimneys of the Poolbeg power station all the way over to Dun Laoghaire harbour.

The rear of the house is north-facing but with one of the best views of Dublin Bay.

When Ruth and Tom Jenkinson fell in love with and bought the original property in 2017, it was an E-rated dwelling with a small 1980s style extension that hadn’t been lived in for some time. But they quickly commissioned Trevor Dobbyn of Fabrica Architects with a brief for a modern, well-insulated house that maximised the view, and which needed minimal maintenance. It also needed to be adaptable to living on the ground floor.

The accommodation brief was achieved by a short, single-storey extension to the front and a generous two-storey extension to the rear, while also being retrofitted to an A3 building energy rating (BER).

Naturally the aim was to open up those amazing views, so the primary challenge was how to offset the large amount of glazing that would be needed at the north-facing rear with the potential for heat loss. “Therefore, the overall performance of the building was of equal importance to the quality of the interior looking out onto Dublin Bay,” says Dobbyn.

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Having worked for the prestigious Dublin based practice de Blacam & Meagher Architects since qualifying in 1997, Dobbyn was one of the first to enroll in DIT’s diploma in thermal bridge assessment in 2013, which he followed up in 2016 with the same institution’s professional energy skills in NZEB course, and also the RIAI environmental accreditation.

“It’s very difficult to un-see a thermal bridge once you’ve learned about them,” he says. Before that, “the kind of physical performance of the building would have been further down the list originally when you’re doing designs, so when you learn that kind of skill, it lends itself to trying to balance a building that’s as efficient as possible but is also aesthetically pleasing.

“So, there’s a bit of a trade-off depending on what you’re trying to achieve... some bits you might feel the design is worth pushing more than the thermal performance and vice versa. You’re trying to detail it so you’re not causing thermal bridges... and you can be kind of restricted in how it looks if you’re just purely going for thermal performance.” This approach explains details like the slender pillars at the front, supporting the large canopy and covered entrance that gives vital shading at the south-facing facade, but which lightens the look and closely matches the shape and feel at the rear.

“The use of shading canopies and projections allows the front and rear elevations to be broken into more slender forms,” Dobbyn says. “They are outside the insulation envelope so they can be much lighter. While the rear canopy is technically not for solar shading, it is angled to face Dun Laoghaire harbour, and allow the owner to have his morning coffee in shelter, while also allowing me to hide the parapet above the sliding doors.”

The 1960s semi-D is of a solid-block construction, so in order to maintain the consistency in terms of the construction materials and method, it made sense to opt for a masonry build for the extension, with the whole shell wrapped in EPS external insulation, finished with an acrylic external render.

Other fabric measures included passive certified, triple glazed timber alu-clad windows all round (with exception of the rooflights), and insulated stone floors with underfloor heating, while the pitched roof was rebuilt with new counter battens, airtight membrane and Xtratherm insulation boards.

The garden is fairly small, but another touch was to install a pillarless safety glass wall at the end to preserve the view, particularly from a sitting position.

A 12 kW Panasonic Aquarea air source heat pump handles the heating duties, while a Lunos E2 demand-controlled heat recovery system looks after ventilation. Supplied by Galway firm Partel, it’s a decentralised ventilated system with automated humidity control.

It was chosen because it is a ductless, self-contained system, mitigating the need to do extensive modifications to install ductwork, particularly given the steelwork required for the extension.

Coming from a traditional gas boiler and central heating system, the adjustment to this new heating-and-ventilation arrangement took a while for the Jenkinson’s. “It is simple to operate. You choose the temperature you want at each room thermostat and the machine does the rest,” says Ruth. “It takes longer to build up or reduce the heat than a gas boiler system.”

She adds that the ventilation certainly enhances the air quality but is audible. The final airtightness test was delayed pending the arrival of a new front door, so results were not available at the time of writing, but Dobbyn reports that while access to the relevant points in the building for airtightness measures was OK, some areas were a little tricky to get at, such as where there the roof rafters met the adjoining property, and the existing first floor joists.

In all, the build progressed fairly smoothly starting in May 2018 and finishing in April 2019, although the completion was delayed because the windows were some six weeks late.

“We were thrilled with the layout, ambience and the modern comforts,” says Ruth. “We were particularly pleased with the upstairs sitting room and the added brightness it gives to that level of the house. “Living in it has been a joy. We installed solar panels but we’re not sure how cost effective they are and perhaps we need more panels. We certainly have a warm and comfortable home and the bills reflect a modern build.”

We were thrilled with the layout, ambience and the modern comforts.

Dobbyn is happy that the final result has achieved that vital balance between energy performance and design that completely fulfils the brief. “The clients have confirmed no issues with the storms during the year with the extent of glazing to the rear, and the view is just incredible,” says Dobbyn.

If the Jenkinson’s have been confined to this home during the Covid-19 lockdown, you can certainly think of worse places to be.

• The front and rear facades of the 1960s semi-detached house prior to renovation The front and rear facades of the 1960s semi-detached house prior to renovation
• The front and rear facades of the 1960s semi-detached house prior to renovation The front and rear facades of the 1960s semi-detached house prior to renovation
• Work underway on removing the existing small extension and windows at the rear of the house Work underway on removing the existing small extension and windows at the rear of the house
• Works carried out during the renovation included rebuilding the original pitched roof Works carried out during the renovation included rebuilding the original pitched roof
• The new two-storey extension at the rear was designed to maximise the spectacular views across Dublin Bay, despite being north-facing The new two-storey extension at the rear was designed to maximise the spectacular views across Dublin Bay, despite being north-facing
• Underfloor heating installed throughout the ground floor Underfloor heating installed throughout the ground floor
• Pro clima Intello membrane to extension ceiling and roof window opening, with airtightness taping Pro clima Intello membrane to extension ceiling and roof window opening, with airtightness taping
• Pro clima Intello membrane to extension ceiling and roof window opening, with airtightness taping Pro clima Intello membrane to extension ceiling and roof window opening, with airtightness taping
• New alu-clad triple-glazed sliding doors were installed to the garden extension New alu-clad triple-glazed sliding doors were installed to the garden extension
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Image gallery

• Ground floor Ground floor
• First floor First floor
• Attic roof Attic roof
• Elevations 1 Elevations 1
• Elevations 2 Elevations 2
• Door threshold Door threshold
• Canopy details Canopy details
• Front wall detail Front wall detail
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